docs: def get_upstream_causal_subgraph(graph, nbunch: Union[BaseEntity, Iterable[BaseEntity]]):
      """Induce a sub-graph from all of the upstream causal entities of the nodes in the nbunch.
  
      :type graph: pybel.BELGraph
      :rtype: pybel.BELGraph
      """
      return get_subgraph_by_edge_filter(graph, build_upstream_edge_predicate(nbunch))